Routing outbound network traffic from a logical router to multiple active edge systems requires that each edge system learn the same routing information at substantially the same time. Having the same routing information allows the logical router to route network traffic to any one edge system without needing to consider whether that edge system has the routing information necessary to properly route the network traffic. If a first edge system does not receive routing information that is received by another edge system, then the first edge system cannot route network traffic that requires the not-received routing information. That network traffic therefore gets stopped at the first edge system and never makes it to its intended destination.
Communication protocols exist that allow edge systems to all receive routing information concurrently. The Border Gateway Protocol (BGP) runs on Internet Protocol and allows IP network routers to advertise routing information to connected peers (e.g., edge systems). While BGP does a good job of ensuring routing information is distributed, situations may arise where BGP communications are disrupted with one or more edge systems. Any routing information that changes and is advertised during that disruption is not received by the affected edge systems, which can cause the routing issues mentioned above.